The investigation is made to determine whether the analogs of hycanthone IA-3, IA-3-N-oxide, IA-4, and IA-4-N-oxide, which still possess antischistosomal activity but are less mutagenic than the parent compound in Salmonella typhimurium, exert similar reduced mutagenic properties in Escherichia coli. This comparison will determine the appropriate bacterial indicators to be used for specific classes of chemicals and will allow a test of the structure-action relationships between mutagenic agents. Finally, should the compounds tested be less mutagenic than hycanthone in E. coli, additional information would be provided on the reduced probability of inducing gene mutations in treated humans.